* Pneumatic Governor Diaphragm *

[philip]

With various sources (including the FSM supplement) saying cod liver oil was the thing to use as a leather preservative on the pneumatic governor diaphragm, I followed that advice.

"Experience is the best teacher"

Today I decided to install that new pneumatic governor diaphragm I've had sitting on the shelf for a couple of months. You can get one of these at a good price at:

http://www.southwestdiesel.com/


What I found after removing the diaphragm cover is the subject of this post. Let me say that I had this cover off about a year ago so I -know- what shape it was in then. Apparently the food grade cod liver I used is not the cod liver oil one would get expressly for the purpose of preserving this governor diaphragm.

The semi hard rubbery black tar I found was unbelievable. See pictures.

This stuff had migrated all over the diaphragm, making it significantly less flexible than its new replacement. The tar also made its way between the fuel control lever and the governor housing resulting in a rather sluggish lever movement. I spent time with Q-tips and petro solvent doing clean up.

This time around, I'm using shoe leather oil (petroleum) and hoping for better results.

The FIRST thing I've noticed with the new diaphragm in place is the engine has MUCH snappier throttle response. Gee ... any wonder?

-Philip

[philip]

With various sources (including the FSM suppliment) saying cod liver oil was the thing to use as a leather preservative on the pneumatic governor diaphragm, I followed that advice.
SNIP
-Philip

Followup. It's been about 5-6k miles since installing the new pneumatic governor diaphragm, treated with RedWing shoe oil.

I removed the diaphragm cover today to see what there was to see.

The excess shoe leather oil was very dark brown and laying on the bottom of the housing. There was also a faintly noticeable cod liver oil aroma, possibly from the previous mishap. The oil residue had thickened and somewhat gummed up the free action of the fuel control lever again. Hmmm

Long and short of this cod liver oil vs. shoe leather oil experience is this: When you replace this diaphragm, smear a very thin, light coating of high quality Vasiline on the leather. Disregard the FSM instruction to add 3cc of oil via the little filler plug.

Any cod oil or leather oil will gum up the fuel control lever and the mechanical governor link lever bushings.

[asavage]

For the site's search (text):

Southwest Diesel & Electrical Corporation
1830 N 27th Ave
Phoenix, AZ 85009-2614

602.269.2471
800.658.5806
602.233.1017 fax

Part No. 155020-7920 ($24.27 + $7 freight to LA)

[ecomike]

For the record here I recently used White Petrolatum, otherwise commonly known as Vaseline(RTM), to lightly coat the leather diaphragm during installation of the new diaphragm in the Injection Pump on my SD-22. Several days later I added 4 ml of virgin Seargent Welch lab grade vacuum pump oil to oil the fill port for the diaphragm.

This oil is designed for use in laboratory vacuum pumps, under vacuum conditons and at elevated temperatures. It is designed not to harden (polymerize) and not to react with other materials. Therefore I have high hopes for the life of this diaphragm.

My thanks to Philip for the early warning about certain other "leather lubricants" and their hardening problems when used on these leather diaphragms.

I will be watching for any performance problems like those Philip experienced and documented, but I suspect that the two lubricants I have chosen and used will not dry out or harden like others have. I also do not think they will harm the leather.

Part of my reasoning on this is that I think the "volatile" part of the leather oil Philip used, evaporated under vacuum and heat conditions and dryed or polymerized the oil. The oil I have used is designed for low vacuum and high heat conditions and is designed to not evaporate or dry out.

The experiment is under way!!!!!!

and only Time will tell!

Happy Motoring!!!!!!

[Zoltan]

Phillip

I really appreciate your taking the time and effort for sharing this kind of information so willingly... I just called the local dealer here in HI, and they charge close to $50 for the same diaphragm.

[philip]

Phillip

I really appreciate your taking the time and effort for sharing this kind of information so willingly... I just called the local dealer here in HI, and they charge close to $50 for the same diaphragm.

It's a hobby both the truck and this website experience.

$50 is not all that bad when you consider how much ocean there is between you and the mainland.

In the beginning, I got a quote of nearly $100 for that diaphragm from a place in Los Angeles!

-Philip

[dieselscout80]

Philip

What are the symptoms of a cracked diaphragm?

I have a 1980 IHC Scout Diesel that came with a SD33T, but when it blew up I installed a SD33 from a US Airforce air plane CJ10A tug. The Tug SD33 uses the MZ govenor like the SD22 in the Datsun/Nissan 720 pickup. I have started having fuel starvation issues. I replaced the priming pump with a new Bosch pump and that helped for a day or two, but it keeps coming back and now it only makes it about a block before cutting out like it is not getting fuel. I wonder if it could be the diaphragm or a vacuum line issue. My air and fuel filters are clean.

Thanks

Carey

[dieselscout80]

Philip what are the symptoms of a cracked diaphragm?

I have a 1980 IHC Scout Diesel that came with a SD33T, but when it blew up I installed a SD33 from a US Air Force air plane CJ10A tug. The Tug SD33 uses the MZ governor like the SD22 in the Datsun/Nissan 720 pickup. I have started having fuel starvation issues. I replaced the priming pump with a new Bosch pump and that helped for a day or two, but it keeps coming back and now it only makes it about a block before cutting out like it is not getting fuel. I wonder if it could be the diaphragm or a vacuum line issue. My air and fuel filters are clean.

Thanks

Carey

[philip]

Philip what are the symptoms of a cracked diaphragm?

The diaphragm is made of leather so it "tears." Increasing vacuum pulls the fuel rack toward low fuel delivery while low vacuum allows the diaphragm spring to push the fuel rack toward maximum fuel delivery. So any leakage through the diaphragm will result in more fuel delivery than optimal.

I have a 1980 IHC Scout Diesel that came with a SD33T, but when it blew up I installed a SD33 from a US Air Force air plane CJ10A tug. The Tug SD33 uses the MZ governor like the SD22 in the Datsun/Nissan 720 pickup. I have started having fuel starvation issues. I replaced the priming pump with a new Bosch pump and that helped for a day or two, but it keeps coming back and now it only makes it about a block before cutting out like it is not getting fuel. I wonder if it could be the diaphragm or a vacuum line issue. My air and fuel filters are clean.

Thanks

SD22/25 in USA use the RDB-MZ pump which has the additional RPM limiting flyweight governor. The MZ has only the pneumatic governor.



See Fuel Filters specifically about bleeding air from the inline pump.

If or when you discover that fuel cannot be pumped out the bleed bolts with some authority, then you need to determine why fuel is not getting to your new filters and / or why fuel is restricted leaving the fuel tank.

When you are SURE there is adequate fuel volume using the hand primer on the lift pump, then the correct position of the Fuel Control Lever needs to be verified.

See Smoke Setscrew and note the RUN position occurs with the Fuel Control Lever perfectly verticle. Anything to the left of verticle is on the way to OFF. With no linkages attached to the FCL, the lever will self center (spring loaded) to the RUN position. BUT ... the RUN position can be fine tuned.

[asavage]

Hello, Carey:

Cracked diaphragm = overfuelling at all but full throttle, and lots of black smoke. Stiff diaphragm (does happen) = poor throttle response, and I guess maybe surging -- Philip is the expert here.

For fuel starvation, it's relatively easy to diagnose this kind of thing. But you do need length of clear tubing and a special tool:



That one's $20 at Sears; you can buy them in the $14-40 price range anywhere, including the discount places. It reads both vacuum and low pressure.

First, use the clear tubing and graft it into one of the lines. I don't know that it's particularly important which one, but I think I'd start at the IP return line or the injectors return line. Run engine, watch for bubbles. Shouldn't be any. If you see some, look for leaks on the vacuum (suction) side of the lift pump and back to the primary filter, then the line to the tank, the rubber line at the top of the tank, and finally the tank pickup tube (on old Ford diesel trucks, the pickup tube breaks off in the tank and you can't run with less than 1/2 tank of fuel!).

No bubbles?

Tee into the line running into the primary filter, duct-tape the gauge to the windscreen, and drive. Pressure goes into vacuum more than 2"? Restriction in the line to the tank, in the tank itself, or the tank venting.

[Related digression No. 1: I had a mud-plugged vent line on an '80 VW Rabbit diesel several years ago. I could drive and drive and drive, and the fuel gauge wouldn't drop below 1/4 tank -- and eventually I'd run out of fuel. Turned out the lift pump was providing enough vacuum to collapse the fuel tank -- the bottom of the tank was weakest, so it'd get pulled up, and the sending unit's float would naturally go up with it. Took me forever to find that one -- and a couple of times running out of fuel on I-5 in the middle of nowhere provided some incentive! The fuel tank has an anti-spill valve to prevent fuel from venting in the event of a rollover. From that valve the vent line runs all the way from the fuel tank in the rear to the . . . front bumper. I kid you not. And somehow (!) that rubber hose at the front bumper got plugged solid with mud. I don't even want to know.

Related digression No. 2: See also the Ford Pickup/paper towel story.]

No vacuum? Move the tee between the primary filter and the lift pump, repeat. Should see pressure there, quite a bit actually. I'll throw out a number and say that anything over 3 PSI is fine.

Then move the tee between the secondary filter and the IP. Should see the same pressure at the last test. If not, restricted secondary filter.

If you get that far, you have fuel to the IP under pressure and you're still getting the "fuel starvation" symptom, the problem either isn't fuel starvation after all, or it's internal to the IP.

[philip]

SNIP
Part of my reasoning on this is that I think the "volatile" part of the leather oil Philip used, evaporated under vacuum and heat conditions and dryed or polymerized the oil. The oil I have used is designed for low vacuum and high heat conditions and is designed to not evaporate or dry out.

The experiment is under way!!!!!! and only Time will tell!

Happy Motoring!!!!!!

Ok, it's been 3-1/2 months. Time to take a look-see!

[ecomike]

Update:

So far its "No Worries Mate".

Regarding the IP leather diaphragm, the vacuum pump oil and vaseline lube experiment I tried when installing the new leather diaphragm, I have not experienced any degradation in performance, yet! So far so good.

[asavage]

It runs OK, but what's the diaphragm look like? When you get caught up . . .

(philip) Yeah ... come on, need a closeup photo or two with the cover off. Goo factor!

[ecomike]

My father had a saying that has grown on me over the years. IF IT AIN'T BROKE, DON'T FIX IT.I did not understand it then, when I got my first set of wheels. I couldn't wait to fix, open, examine, play with, things that wheren't broke then.

OK,

If everything else quits quiting on me long enough....

But as I recall, Philip already had major sluggish performance after 3 months with both of his first diaphragm oils (both were Cod liver oils, right?).

[philip]

SNIP
But as I recall, Philip already had major sluggish performance after 3 months with both of his first diaphragm oils (both were Cod liver oils, right?).

The throttle response deterioration was slow enough that I was not really aware of how lethargic it had become until AFTER I repaired the 'polymerized" state of the diaphragm.